THE PROCESS OF MEIOSIS

Meiosis is a special type of cell division that occurs in the gonads or sex organs.

• At the end of meiosis, the number of chromosomes is reduced by half. That is, meiosis of diploid cells produces haploid daughter cells.
• These cells can then function as gametes that can undergo fertilization resulting in the restoration of the diploid number of chromosomes in the zygote.
• Meiosis and fertilization introduce genetic variation in three ways:

The meiosis consist of two main stages:

•  Meiosis I: This is made up of four sub-stages: Prophase I, Metaphase I, Anaphase I and Telophase I
•  Meiosis II: This is made up of four sub-stages: Prophase II, Metaphase II, Anaphase II and Telophase II

You can click on this link to view a diagram on the meitotic process. This will help you to visualize the steps described below.

MEIOSIS I

Prophase I  The chromosomes condense and become visible. The centrioles form and move toward the poles. The nuclear membrane begins to dissolve. The homologs pair up, forming a tetrad.  Each tetrad is comprised of four chromotids - the two homologs, each with their sister chromatid. Genetic material from the homologous chromosomes is randomly swapped. This process is known as crossing over.  Crossing over increases genetic diversity by creating four unique chromatids.

Metaphase I Microtubules grow from the centrioles and attach to the centromeres The tetrads line up along the cell equator.

Anaphase I The centromeres break and homologous chromosomes separate with the sister chromatids are still attached. Cytokinesis begins.

Telophase I The chromosomes may decondense. Cytokinesis reaches completion, creating two haploid daughter cells

MEIOSIS II 

Prophase II Centrioles form and move toward the poles. The nuclear membrane dissolves.

Metaphase II Microtubules grow from the centrioles and attach to the centromeres. The sister chromatids line up along the cell equator.

Anaphase II The centromeres break and sister chromatids separate.  Cytokinesis begins.

Telophase II The chromosomes may decondense. Cytokinesis reaches completion, creating four haploid daughter cells.